1. Field of the Invention
The present invention relates to a coupling which is disposed in a torque-transmitting path and which is fastened by an electromagnetic control.
2. Description of Relevant Art
There has been disclosed a coupling in xe2x80x9cGaia new type car explanation (published on May 29, 1998 by Toyota automobile Co., Ltd. service department)xe2x80x9d.
In the above-mentioned coupling, a control clutch and a main clutch are arranged in series in a rotational axis direction, and the coupling is elongated in the axial direction.
An object of the invention is to provide a coupling in which a length in an axial direction is shortened.
From an aspect of the present invention, there is provided a coupling as follows. The coupling includes a first clutch, and a second clutch for controlling fastening and releasing operation of the first clutch. The first clutch and the second clutch are radially differently and axially correspondently positioned each other.
According to the invention, the coupling becomes small-sized in an axial direction, and a freedom on design is improved. Therefore, a coupling which needs a transmission torque capacity for an insufficient axial space, such as a start clutch for a vehicle disposed between a motor (an engine) and a transmission, obtains a preferable constitution.
The term of xe2x80x9cfirst clutchxe2x80x9d means a main clutch including a single plate clutch or a plurality of plates clutch. For example, the main clutch includes inner plates and outer plates, and a thrust washer. The term of xe2x80x9csecond clutchxe2x80x9d means a pilot clutch including a single plate clutch or a plurality of plates clutch. For example, the pilot clutch includes including inner plates and outer plates, and an armature. The term of xe2x80x9ccontrollingxe2x80x9d includes not only an intermediate control of a clutch fastening force, or a transmission torque, but also a switching operation between fastening and releasing of a clutch. The phrase of xe2x80x9caxially correspondently positionedxe2x80x9d includes a meaning that an axial position of a part of the first clutch corresponds to an axial position of a part of the second clutch.
Preferably, the first clutch is disposed radially outward of the second clutch.
According to the invention, a torque capacity of a clutch is enlarged. As a result, for example, in multi-disc plates type clutch, it is possible to reduce the number of clutch plates for obtaining the same torque capacity, thus to further easily reduce an axial size of a coupling.
Preferably, the second clutch is to be magnetically operated.
According to the invention, it is carried out with a simple structure in comparison with that for operating a second clutch by an oil pressure system, and a transmission torque of a coupling is accurately controlled.
Preferably, the coupling further includes an electromagnet which is axially adjacent to the second clutch.
According to the invention, the second clutch is directly operated, and an operation response of a coupling is largely improved in comparison with, for example, a constitution for operating a second clutch through an intermediate member.
Preferably, the coupling further includes an amplifying mechanism for amplifying a transmitted torque and converting the transmitted torque to an operating force, the transmitted torque to be applied to the amplifying mechanism when fastening the second clutch.
According to the invention, the amplifying mechanism makes an operating force of the first clutch amplified, and a torque transmission capacity between the first clutch and the coupling are strengthened. The first clutch and the coupling becomes small-sized and light.
Preferably, the amplifying mechanism and the first clutch are radially correspondently positioned each other.
According to the invention, the amplifying mechanism and the first clutch are axially arranged each other, and the coupling becomes radially small-sized. The phrase of xe2x80x9cradially correspondently positionedxe2x80x9d includes a meaning that a radial position of a part of the amplifying mechanism corresponds to a radial position of a part of the first clutch.
Preferably, the amplifying mechanism and the second clutch are radially correspondently positioned each other.
According to the invention, the amplifying mechanism and the second clutch are axially arranged, and the coupling is radially small-sized.
Preferably, the amplifying mechanism includes a lever mechanism radially extending, the lever mechanism to be swung about a fulcrum in a middle part thereof.
According to the invention, to select a fulcrum position of the lever mechanism allows an amplifying rate of an operating force to be easily changed.
Preferably, the amplifying mechanism includes a lever mechanism fixed with a diaphragm-type spring at a radially outward end thereof for pressing the first clutch, the lever mechanism to be swung about a fulcrum in a middle part thereof.
According to the invention, for example, it is possible to adopt a constitution in which the diaphragm-type spring makes the first clutch mechanically pressed and fastened, and the amplifying mechanism is employed for releasing the first clutch, thus to set an operating force source small at the release. Therefore, it is remarkably advantageous to use for fastening the first clutch in most of operation time.
Preferably, the amplifying mechanism is disposed radially inward of the first clutch and the second clutch.
According to the invention, the amplifying mechanism is disposed at a position close to a rotational axis and radially inward of the first clutch and the second clutch, and a torque to be applied to the amplifying mechanism is enlarged. Therefore, a torque transmission capacity between the first clutch and the amplifying mechanism are further strengthened, and these sizes and weights are reduced.
A large torque is applied to the amplifying mechanism, and a response for generating an operating force of the first clutch is improved.
In a constitution employing the lever mechanism for an amplifying function, by disposing the amplifying mechanism at a position close to the rotational axis, a lever is lengthened for that, and an extent to be selected for a swing fulcrum is widened. Therefore, a torque transmission capacity between the first clutch and a coupling is further strengthened.
Preferably, the first clutch is disposed radially outward of the second clutch. The coupling further includes an operating member for transmitting an operating force amplified by the amplifying mechanism to the first clutch.
The operating member has a base part and an operating part for the first clutch formed at an outer end of the base part. The operating part axially opposes to the first clutch. The base part is connected with the amplifying mechanism and the operating part over the second clutch.
According to the invention, the coupling is further radially small-sized in comparison with a constitution in which an operating member is radially disposed.
Preferably, the coupling further includes an operating member for transmitting an operating force amplified by the amplifying mechanism to the first clutch. The amplifying mechanism is provided between the operating member and a first clutch side member.
According to the invention, an operating force of the first clutch is cancelled inside the first clutch, and the operating force is not applied to outer members around the first clutch, so that durability is largely improved.
For example, without a thrust bearing to be subjected to an operating force between the first clutch side member and an outer member to relatively rotate each other, they are not self-locked without, and the thrust bearing is not necessary. Thus, a cost is reduced for that, a constitution is small-sized, and a freedom on design is improved.
Preferably, the amplifying mechanism is a cam mechanism.
According to the invention, the cam mechanism is small-sized and generates a large operating force, so that a torque transmission capacity between the first clutch and a coupling is further strengthened without increment of an arrangement space.
Preferably, the coupling further includes a torque transmission member connected with the first clutch and the second clutch. The torque transmission member has a first and a second cylinder part. The first cylinder part is connected with the first clutch. The second cylinder part is connected with the second clutch.
According to the invention, the first clutch and the second clutch are connected to the first and second cylinder parts formed to the identical torque transmission member. Thus the number of constitution members is reduced and the coupling becomes small-sized and light in comparison with a constitution in which they each are connected to a different torque transmission member.
Especially, in the invention where the first clutch and the second clutch are radially arranged, the coupling is axially small-sized.
Preferably, the coupling further includes a torque transmission member connected with the first clutch and the second clutch. The torque transmission member has a cylinder part with a first and a second side. The first clutch is connected to the first side. The second clutch is connected to the second side.
According to the invention, the first clutch and the second clutch are connected respectively to the first side and the second side in a radial direction, and they are radially arranged.
The first clutch and the second clutch are connected to the identical cylinder part of the torque transmission member, and the torque transmission member becomes small-sized and light.
Preferably, the second clutch is a cone clutch.
According to the invention, the cone clutch with the small number of friction faces makes a pulling force small at release of fastening, in comparison with a multi-disc plates clutch with the large number of friction faces.
For example, in a coupling which employs a cone clutch for an automatic clutch of an automatic transmission vehicle, if it is structured to use under a wet environment with ATF (Automatic Transmission Oil) for lubrication and cooling, a pulling force is small, a noise level is remarkably small and a torque is substantially completely removed, so that smooth transmission is achieved.
A volume of a synchronous mechanism becomes small, and a cost for that is reduced.
As employing an oil pump for an automatic transmission, an exclusive oil pump for a coupling and a device for lubrication and cooling are omitted, and a cost is further reduced.
Preferably, the first is fastened while releasing the second clutch.
According to the invention, for example, with a constitution in which a diaphragm type spring presses the first clutch to be normally fastened, the second clutch is operated for fastening only when releasing the first clutch.
A lever mechanism amplifies an operating force for releasing the first clutch, and a fastening force of the second clutch becomes small. As a result, it is possible to save energy, a durability of an electromagnet is improved, an electromagnet becomes small-sized, and a load of a battery is reduced.